FETCh and MEASure Subsystems
The FETCh and MEASure subsystems return measured data. The FETCh and MEASure queries do not take any
parameters, and they have the identical syntax (such as FETCh:VOLTage:AC? and MEASure:VOLTage:AC?).
Measurements may be acquired continuously or non-continuously, as specified by
.
The *RST and *RCL commands disable continuous operation.
Non-continuous measurement mode
MEASure Subsystem
A MEASure query or an IMMediate or BUS trigger generates a new measurement that is stored in a buffer and then
returned to the user.
Before the instrument can accept an IMMediate or BUS trigger, you must first send INITiate:ACQuire. Otherwise,
the instrument will generate SCPI error -211,"Trigger ignored" . The buffer retains the measured data until cleared
by another MEASure query, an accepted IMMediate or BUS trigger, a *RST or INITiate:ACQuire command, or a
power cycle.
FETCh Subsystem
A FETCh query immediately returns the previously acquired measurement from this buffer. If no measurement is in
the buffer, the instrument generates SCPI error -230,"Data corrupt or stale".
General Measurement Operation
Data acquisition occurs at 333 ms intervals, which includes a digitization aperture of 100 to 125 ms. If there are no
MEASure queries or triggers, the data is discarded.
When a MEASure query or IMMediate or BUS trigger is received, the instrument waits for the current digitization to
finish, discards the data, and waits for the next measurement interval to finish. The instrument then stores the next
measurement into the buffer to ensure that the entire measurement was sampled after the MEASure query or
IMMediate or BUS trigger. Therefore, a measurement could require from 333 to 666 ms to complete.
The acquired measurement includes both the instantaneous voltage and current. The FETCh query may return any
calculated measurement item derived from this data, including FETC:CURR:DC?, FETC:VOLT:AC?, and
FETC:POW:ACDC?.
For averaged measurements of 2, 4, 8, or 16 intervals, the instrument stores and averages multiple measurements.
Therefore, a measurement could take up to 17 x 333 ms to complete.
Continuous measurement mode
Internal data acquisition occurs at 333 ms update intervals, including the aperture as described above, and each
completed measurement overwrites the previous data in the buffer. Averaged measurements are a moving average
of the latest 2, 4, 8, or 16 measurements.
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Keysight AC6800 Series Operating and Service Guide
